most but not all gew 88's have a .318 barrel, some where rebarreled to .323 most if not all 7.62 are .310 so you would have a difference of .008 not much but it would affect accuracy plus the rim diminsion is smaller

I shoot my Commisson rifle all the time, I use woodleigh 318 round nose, load weak, and plink all day. I would never ever ever use 8mm mauser .323, some say you can I will no.t also even if rebarreled to .323 the pressure of modern service ammo is to much